This research is focused on the calculation of a reasonable detonator delay time for realizing cut blast vibration control.First,the viscoelastic rock mass parameters corresponding to the engineering rock mass quality...This research is focused on the calculation of a reasonable detonator delay time for realizing cut blast vibration control.First,the viscoelastic rock mass parameters corresponding to the engineering rock mass quality classification were determined based on wave theory of Kelvin medium.Then,a calculation model was obtained for the millisecond-delay cut blast vibration in Kelvin media using the Starfield charge superposition principle.Further,the influence of the delay time on the cut blast vibration was quantitatively analyzed and a method for calculating the reasonable cut blasting millisecond delay time is proposed according to the principle of dimensional analysis.Finally,field tests were used to verify the applicability of the method.The results show that 5 ms to 20 ms is a better detonator delay time range and cut blasting vibration can be effectively controlled using the delay time calculated by the calculation model described in this paper.展开更多
The roller is one of the fundamental elements of ore belt conveyor systems since it supports,guides,and directs material on the belt.This component comprises a body(the external tube)that rotates around a fixed shaft ...The roller is one of the fundamental elements of ore belt conveyor systems since it supports,guides,and directs material on the belt.This component comprises a body(the external tube)that rotates around a fixed shaft supported by easels.The external tube and shaft of rollers used in ore conveyor belts are mostly made of steel,resulting in high mass,hindering maintenance and replacement.Aiming to achieve mass reduction,we conducted a structural optimization of a roller with a polymeric external tube(hereafter referred to as a polymeric roller),seeking the optimal values for two design parameters:the inner diameter of the external tube and the shaft diameter.The optimization was constrained by admissible values for maximum stress,maximum deflection and misalignment angle between the shaft and bearings.A finite element model was built in Ansys Workbench to obtain the structural response of the system.The roller considered is composed of an external tube made of high-density polyethylene(HDPE),bearing seats of polyamide 6(PA6),and a steel shaft.To characterize the polymeric materials(HDPE and PA6),stress relaxation tests were conducted,and the data on shear modulus variation over time were inserted into the model to calculate Prony series terms to account for viscoelastic effects.The roller optimization was performed using surrogate modeling based on radial basis functions,with the Globalized Bounded Nelder-Mead(GBNM)algorithm as the optimizer.Two optimization cases were conducted.In the first case,concerning the roller’s initial material settings,the designs found violated the constraints and could not reduce mass.In the second case,by using PA6 in both bearing seats and the tube,a design configuration was found that respected all constraints and reduced the roller mass by 15.5%,equivalent to 5.15 kg.This study is among the first to integrate experimentally obtained viscoelastic data into the surrogate-based optimization of polymeric rollers,combining methodological innovation with industrial relevance.展开更多
We investigated the influence of historical earthquakes on the 2022 Luding M_(S)6.8 earthquake and its subsequent effects.We computed the viscoelastic Coulomb stress changes induced by these historical seismic events ...We investigated the influence of historical earthquakes on the 2022 Luding M_(S)6.8 earthquake and its subsequent effects.We computed the viscoelastic Coulomb stress changes induced by these historical seismic events using the rupture model of historical earthquakes and the layered Maxwell viscoelastic medium model.Our findings indicate that the Luding earthquake was brought forward approximately 29 years because of several historical earthquakes.Specifically,the 1923 Renda M_(S)7.3 earthquake,the 1933 Diexi M_(S)7.5 earthquake,the 1973 Luhuo M_(S)7.3 earthquake,the 2008 Kangding M_(S)5.1 earthquake,the 2008 Wenchuan M_(S)8.0 earthquake,the 2014 Kangding M_(S)6.3 earthquake,and the 2014 Kangding M_(S)5.8 earthquake advanced the occurrence of the event by 117.61,26.67,84.51,0.27,0.91,7.64,and 3.17 years,respectively.Conversely,the 1936 Mabian earthquake swarm,the 1948 Litang M_(S)7.3 earthquake,the 1955 Kangding M_(S)7.5 earthquake,and the 2013 Lushan M_(S)7.0 earthquake delayed its occurrence by 39.89,22.43,144.23,and 4.89 years,respectively.Furthermore,by employing the halfspace homogeneous elastic model and the rupture characteristics of the Luding earthquake,we computed the coseismic Coulomb stress changes in neighboring faults.Our results reveal increased Coulomb stress on the Xianshuihe fault(excluding its southern segment),the Anninghe fault,the Zemuhe fault,the Daliangshan fault,the southern segment of the Longmenshan fault,the northern segment of the Mabian-Yanjin fault,and the Xiaojinhe fault.Conversely,we observed stress decreases in the southern segment of the Jinshajiang fault,the central and eastern segments of the Longriba fault,the Mabian-Yanjin fault(excluding its northern segment),and the southern segment of the Xianshuihe fault.展开更多
The formation of copper deposits is closely related to hydrothermal processes.Understanding the migration of copper in hydrothermal fluids aids in reconstructing mineralization processes and deciphering deposit genesi...The formation of copper deposits is closely related to hydrothermal processes.Understanding the migration of copper in hydrothermal fluids aids in reconstructing mineralization processes and deciphering deposit genesis.Copper primarily exists as Cu^(+)and Cu^(2+)in hydrothermal solutions,with redox conditions governing their interconversion.In chloride-rich geological fluids,Cu-Cl complexes are considered critical for copper transport.However,the specific types and valence transitions of Cu-Cl complexes under varying hydrothermal conditions remain poorly understood.This study employed in situ Raman spectroscopy to systematically analyze Cu+HCl and CuCl_(2)+K_(2)S_(2)O_(3)/H_(2) systems under saturated vapor pressure at 25-300℃,elucidating the effects of temperature,Cl^(-)concentration,and redox conditions on copper speciation.In the Cu^(+)HCl system,copper dissolved as monovalent Cu-Cl complexes.At high temperatures(>200℃),[CuCl_(2)]^(-)is the dominated species,whereas[CuCl_(3)]^(2-)becomes prevalent at lower temperatures and higher HCl concentrations.For the Cu^(2+)-Cl system,the dominant species transitioned from[Cu(H_(2)O)n]^(2+)(<50℃)to[CuCl_(4)]^(2-)(100℃)and further to[CuCl]^(+)and[CuCl_(2)]^(0) at 300℃.The introduction of reducing agents(K_(2)S_(2)O_(3)/H_(2))facilitated Cu^(2+)→Cu^(+)reduction,thereby stabilizing Cu^(+)-Cl complexes and inducing partial copper precipitation.The behavior of copper in chloriderich hydrothermal fluids observed in this study indicates that high-temperature oxidizing fluids facilitate Cu mobilization,while cooling and redox changes promote deposition and ore minerals formation.展开更多
This study presents and verifies a hybrid methodology for reliable determination of parameters in structural rheological models(Zener,Burgers,and Maxwell)describing the viscoelastic behavior of polyurethane specimens ...This study presents and verifies a hybrid methodology for reliable determination of parameters in structural rheological models(Zener,Burgers,and Maxwell)describing the viscoelastic behavior of polyurethane specimens manufactured using extrusion-based 3D printing.Through comprehensive testing,including cyclic compression at strain rates ranging from 0.12 to 120 mm/min(0%-15%strain)and creep/relaxation experiments(10%-30%strain),the lumped parameters were independently determined using both analytical and numerical solutions of the models’differential equations,followed by cross-verification in additional experiments.Numerical solutions for creep and relaxation problems were obtained using finite element analysis,with the three-parameter Mooney-Rivlin model and Prony series employed to simulate elastic and viscous stress components,respectively.Energy dissipation per cycle was quantified during cyclic compression tests.The results demonstrate that all three models adequately describe material behavior within the 0%-15%strain range across various strain rates.Comparative analysis revealed the Burgers model’s superior performance in characterizing creep and stress relaxation at low strain levels.While Zener and Burgers model parameters from uniaxial compression showed limited applicability for energy dissipation calculations,the generalized Maxwell model effectively captured viscoelastic properties across different strain rates.Notably,parameters derived from creep tests provided a more universal assessment of dissipative properties due to optimization based on characteristic curve regions.Both parameter sets described polyurethane’s elastic-hysteretic behavior with approximately 20%error,proving significantly more accurate than the linear strain-time dependence hypothesis.Finite element analysis(FEA)complemented numerical modeling by demonstrating that while the generalized Maxwell model effectively describes initial rapid stress-strain changes,FEA provides superior characterization of steady-state processes.This computational approach yields more physically representative results compared to simplified analytical solutions,despite certain limitations in transient analysis.展开更多
Supercritical fluids play a crucial role in material transport within Earth's deep interior.Investigating the pressure-dependent atomic structures and transport properties of such fluids is essential for understan...Supercritical fluids play a crucial role in material transport within Earth's deep interior.Investigating the pressure-dependent atomic structures and transport properties of such fluids is essential for understanding their petrological,chemical,and geophysical behaviors.In this study,we employed first-principles molecular dynamics simulations to explore the structures,self-diffusion coefficients(D),and viscosities(η)of supercritical NaAlSi_(3)O_(8)-H_(2)O fluids under conditions of 2000 K and 3-10 GPa,with water contents of 30 wt% and 50 wt%.Our calculations indicate that at a water content of 30 wt%,Q^(2) and Q^(3) exhibit a certain degree of positive and negative pressure dependence,respectively,while other Q^(n) species(n represents the number of bridging oxygens connected to Si/Al)show minimal changes.At a water content of 50 wt%,Q^(2) and Q^(0) exhibit a certain degree of positive and negative pressure dependence,respectively,while other Q^(n) species show minimal changes.At both water contents,Si-O-H and molecular water in the system exhibit negative pressure dependence,suggesting that the migration of supercritical fluids from deep to shallow regions is accompanied by the release of water.The self-diffusion coefficients in the supercritical NaAlSi_(3)O_(8)-H_(2)O fluid follow the order D_(Na)≈D_(H)>D_(O)>D_(Al)≈D_(Si),with an overall weak negative pressure dependence.By comparing the viscosities of anhydrous and hydrous silicate melts from previous studies,we found that the addition of water caused a transition from negative to positive pressure dependence of viscosity,corresponding to a structural change from polymerization to depolymerization.Additionally,we calculated the fluid mobility Δp/η of supercritical NaAlSi_(3)O_(8)-H_(2)O fluids and found that their mobility is several orders of magnitude higher than that of basalt melt and is also significantly greater than that of carbonate melt.As supercritical fluids ascend from deeper to shallower regions,their mobility is further enhanced,significantly contributing to the transport of elements from subducting slabs to the overlying mantle wedge.展开更多
1 INTRODUCTIONIt is well known that viscoelasticity and thixotropy of fluids are often investigated by measuringhysteresis loops under transient conditions.For some fluids(such as blood),it has been provedthat,an“8”...1 INTRODUCTIONIt is well known that viscoelasticity and thixotropy of fluids are often investigated by measuringhysteresis loops under transient conditions.For some fluids(such as blood),it has been provedthat,an“8”shaped hysteresis loop may be obtained if triangular steps of shear rate wereapplied on it(Fig.l).This kind of hysteresis loop is composed of a viscoelastic loop and athixotropic loop.The viscoelastic and thixotropic properties are unified in the formation ofthe hysteresis loop.How to describe the formation of this complex hysteresis loop and how展开更多
This study investigates the electromagnetohydrodynamic(EMHD)flow of fractional viscoelastic fluids through a microchannel under the Navier slip boundary condition.The flow is driven by the pressure gradient and electr...This study investigates the electromagnetohydrodynamic(EMHD)flow of fractional viscoelastic fluids through a microchannel under the Navier slip boundary condition.The flow is driven by the pressure gradient and electromagnetic force where the electric field is applied horizontally,and the magnetic field is vertically(upward or downward).When the electric field direction is consistent with the pressure gradient direction,the changes of the steady flow rate and velocity with the Hartmann number Ha are irrelevant to the direction of the magnetic field(upward or downward).The steady flow rate decreases monotonically to zero with the increase in Ha.In contrast,when the direction of the electric field differs from the pressure gradient direction,the flow behavior depends on the direction of the magnetic field,i.e.,symmetry breaking occurs.Specifically,when the magnetic field is vertically upward,the steady flow rate increases first and then decreases with Ha.When the magnetic field is reversed,the steady flow rate first reduces to zero as Ha increases from zero.As Ha continues to increase,the steady flow rate(velocity)increases in the opposite direction and then decreases,and finally drops to zero for larger Ha.The increase in the fractional calculus parameterαor Deborah number De makes it take longer for the flow rate(velocity)to reach the steady state.In addition,the increase in the strength of the magnetic field or electric field,or in the pressure gradient tends to accelerate the slip velocity at the walls.On the other hand,the increase in the thickness of the electric double-layer tends to reduce it.展开更多
Four typical types of residual oil, residual oil trapped in dead ends, oil ganglia in pore throats, oil at pore corners and oil film adhered to pore walls, were studied. According to main pore structure characteristic...Four typical types of residual oil, residual oil trapped in dead ends, oil ganglia in pore throats, oil at pore corners and oil film adhered to pore walls, were studied. According to main pore structure characteristics and the fundamental morphological features of residual oil, four displacement models for residual oil were proposed, in which pore-scale flow behavior of viscoelastic fluid was analyzed by a numerical method and micro-mechanisms for mobilization of residual oil were discussed. Calculated results indicate that the viscoelastic effect enhances micro displacement efficiency and increases swept volume. For residual oil trapped in dead ends, the flow field of viscoelastic fluid is developed in dead ends more deeply, resulting in more contact with oil by the displacing fluid, and consequently increasing swept volume. In addition, intense viscoelastic vortex has great stress, under which residual oil becomes small oil ganglia, and finally be carried into main channels. For residual oil at pore throats, its displacement mechanisms are similar to the oil trapped in dead ends. Vortices are developed in the depths of the throats and oil ganglia become smaller. Besides, viscoelastic fluid causes higher pressure drop on oil ganglia, as a driving force, which can overcome capillary force, consequently, flow direction can be changed and the displacing fluid enter smaller throats. For oil at pore corners, viscoelastic fluid can enhance displacement efficiency as a result of greater velocity and stress near the corners. For residual oil adhered to pore wall, viscoelastic fluid can provide a greater displacing force on the interface between viscoelastic fluid and oil, thus, making it easier to exceed the minimum interfacial tension for mobilizing the oil film.展开更多
A mixed subgrid-scale（SGS） model based on coherent structures and temporal approximate deconvolution（MCT） is proposed for turbulent drag-reducing flows of viscoelastic fluids. The main idea of the MCT SGS model is...A mixed subgrid-scale（SGS） model based on coherent structures and temporal approximate deconvolution（MCT） is proposed for turbulent drag-reducing flows of viscoelastic fluids. The main idea of the MCT SGS model is to perform spatial filtering for the momentum equation and temporal filtering for the conformation tensor transport equation of turbulent flow of viscoelastic fluid, respectively. The MCT model is suitable for large eddy simulation（LES） of turbulent dragreducing flows of viscoelastic fluids in engineering applications since the model parameters can be easily obtained. The LES of forced homogeneous isotropic turbulence（FHIT） with polymer additives and turbulent channel flow with surfactant additives based on MCT SGS model shows excellent agreements with direct numerical simulation（DNS） results. Compared with the LES results using the temporal approximate deconvolution model（TADM） for FHIT with polymer additives, this mixed SGS model MCT behaves better, regarding the enhancement of calculating parameters such as the Reynolds number.For scientific and engineering research, turbulent flows at high Reynolds numbers are expected, so the MCT model can be a more suitable model for the LES of turbulent drag-reducing flows of viscoelastic fluid with polymer or surfactant additives.展开更多
Particle motion in confined shear flow of viscoelastic fluids is very common in nature and has a wide range of applications.Understanding and mastering the motion characteristics of particles in viscoelastic fluids ha...Particle motion in confined shear flow of viscoelastic fluids is very common in nature and has a wide range of applications.Understanding and mastering the motion characteristics of particles in viscoelastic fluids has important academic value and practical significance.In this paper,we first introduce the related equations and characteristic parameter,and then emphasize the following issues:the lateral equilibrium position of particle;interaction and aggregation of multiple particles;the chain structure formed by multiple particles;and the motion of non-spherical particle.Finally,some unresolved issues,challenges,and future research directions are highlighted.展开更多
Some sufficient conditions of the energy conservation for weak solutions of incompressible viscoelastic flows are given in this paper.First,for a periodic domain in R^(3),and the coefficient of viscosity μ=0,energy c...Some sufficient conditions of the energy conservation for weak solutions of incompressible viscoelastic flows are given in this paper.First,for a periodic domain in R^(3),and the coefficient of viscosity μ=0,energy conservation is proved for u and F in certain Besovs paces.Furthermore,in the whole space R^(3),it is shown that the conditions on the velocity u and the deformation tensor F can be relaxed,that is,u∈B_(3,c(N))^(1/3),and F∈B_(3,∞)^(1/3).Finally,when μ>0,in a periodic domain in R^(d) again,a result independent of the spacial dimension is established.More precisely,it is shown that the energy is conserved for u∈L^(T)(0,T;L^(n)(Ω))for any 1/r+1/s≤1/2,with s≥4,and F∈L^(m)(0,T;L^(n)(Ω))for any 1/m+1/n≤1/2,with n≥4.展开更多
We prove a local existence of a strong solution v ：Ω×T→R^3 for a system of nonlinear integrodifferential equations describing motion of an incompressible viscoelastic fluid using standard mathematical tools. T...We prove a local existence of a strong solution v ：Ω×T→R^3 for a system of nonlinear integrodifferential equations describing motion of an incompressible viscoelastic fluid using standard mathematical tools. The problem is considered in a bounded, smooth domain ΩСR^3 with a Dirichlet boundary condition and a standard initial condition.展开更多
A new generalized Lorenz system is presented based on the thermal convection of Oldroyd-B fluids in a circular loop. Two non-dimensional parameters De1 （a measure of the fluid relaxation） and De2 （a measure of the ...A new generalized Lorenz system is presented based on the thermal convection of Oldroyd-B fluids in a circular loop. Two non-dimensional parameters De1 （a measure of the fluid relaxation） and De2 （a measure of the fluid retardation） appear in the equation. Then we study this generalized Lorenz equation numerically and find that the values of De1 and De2 can greatly influence the behavior of the solution. The fluid relaxation De1 is found to precipitate the onset of periodic solution （limit cycle） in the system and impedes the onset of chaos while the fluid retardation （De2） tends to delay the onset of the periodic solution and precipitate the onset of chaos in the system.展开更多
The conservation of rheological and filtration properties of drilling fluids is essential during drilling operations.However,high-pressure and high-temperature conditions may affect drilling fluid additives,leading to...The conservation of rheological and filtration properties of drilling fluids is essential during drilling operations.However,high-pressure and high-temperature conditions may affect drilling fluid additives,leading to their degradation and reduced performance during operation.Hence,the main objective of this study is to formulate and evaluate a viscoelastic surfactant(VES)to design water-based drilling nanofluids(DNF).Silica nanomaterials are also incorporated into fluids to improve their main functional characteristics under harsh conditions.The investigation included:i)synthesis and characterization of VES through zeta potential,thermogravimetric analysis(TGA),Fourier transform infrared spectroscopy(FTIR),atomic force microscopy(AFM),and rheological behavior;ii)the effect of the presence of VES combined with silica nanoparticles on the rheological,filtration,thermal,and structural properties by steady and dynamic shear rheological,filter press,thermal aging assays,and SEM(SEM)assays,respectively;and iii)evaluation of filtration properties at the pore scale through a microfluidic approach.The rheological results showed that water-based muds(WBMs)in the presence of VES exhibited shearthinning and viscoelastic behavior slightly higher than that of WBMs with xanthan gum(XGD).Furthermore,the filtration and thermal properties of the drilling fluid improved in the presence of VES and silica nanoparticles at 0.1 wt%.Compared to the WBMs based on XGD,the 30-min filtrate volume for DNF was reduced by 75%.Moreover,the Herschel-Bulkley model was employed to represent the rheological behavior of fluids with an R2of approximately 0.99.According to SEM,laminar and spherical microstructures were observed for the WBMs based on VES and XGD,respectively.A uniform distribution of the nanoparticles was observed in the WBMs.The results obtained from microfluidic experiments indicated low dynamic filtration for fluids containing VES and silica nanoparticles.Specifically,the filtrate volume of fluids containing VES and VES with silica nanoparticles at 281 min was 0.35 and 0.04 m L,respectively.The differences in the rheological,filtration,thermal,and structural results were mainly associated with the morphological structure of VES or XGD and surface interactions with other WBMs additives.展开更多
This paper presents ordered rate nonlinear constitutive theories for thermoviscoelastic fluids based on Classical Continuum Mechanics (CCM). We refer to these fluids as classical thermoviscoelastic polymeric fluids. T...This paper presents ordered rate nonlinear constitutive theories for thermoviscoelastic fluids based on Classical Continuum Mechanics (CCM). We refer to these fluids as classical thermoviscoelastic polymeric fluids. The conservation and balance laws of CCM constitute the core of the mathematical model. Constitutive theories for the Cauchy stress tensor are derived using the conjugate pair in the entropy inequality, additional desired physics, and the representation theorem. The constitutive theories for the Cauchy stress tensor consider convected time derivatives of Green’s strain tensor or the Almansi strain tensor up to order n and the convected time derivatives of the Cauchy stress tensor up to order m. The resulting constitutive theories of order (m, n) are based on integrity and are valid for dilute as well as dense polymeric, compressible, and incompressible fluids with variable material coefficients. It is shown that Maxwell, Oldroyd-B, and Giesekus constitutive models can be described by a single constitutive theory. It is well established that the currently used Maxwell and Oldroyd-B models predict zero normal stress perpendicular to the flow direction. It is shown that this deficiency is a consequence of not retaining certain generators and invariants from the integrity (complete basis) in the constitutive theory and can be corrected by including additional generators and invariants in the constitutive theory. Similar improvements are also suggested for the Giesekus constitutive model. Model problem studies are presented for BVPs consisting of fully developed flow between parallel plates and lid-driven cavities utilizing the new constitutive theories for Maxwell, Oldroyd-B, and Giesekus fluids. Results are compared with those obtained from using currently used constitutive theories for the three polymeric fluids.展开更多
The paper explores the gravity-driven flow of the thin film of a viscoelastic-fluid-based nanofluids(VFBN)along an inclined plane under non-isothermal conditions and subjected to convective cooling at the free-surface...The paper explores the gravity-driven flow of the thin film of a viscoelastic-fluid-based nanofluids(VFBN)along an inclined plane under non-isothermal conditions and subjected to convective cooling at the free-surface.The Newton’s law of cooling is used to model the convective heat-exchange with the ambient at the free-surface.The Giesekus viscoelastic constitutive model,with appropriate modifications to account for non-isothermal effects,is employed to describe the polymeric effects.The unsteady and coupled non-linear partial differential equations(PDEs)describing the model problem are obtained and solved via efficient semi-implicit numerical schemes based on finite difference methods(FDM)implemented in Matlab.The response of the VFBN velocity,temperature,thermal-conductivity and polymeric-stresses to variations in the volume-fraction of embedded nanoparticles is investigated.It is shown that these quantities all increase as the nanoparticle volume-fraction becomes higher.展开更多
Viscoelastic nanofluid flow has drawn substantial interest due to its industrial uses,including research and testing of medical devices,lubrication and tribology,drug delivery systems,and environmental remediation.Thi...Viscoelastic nanofluid flow has drawn substantial interest due to its industrial uses,including research and testing of medical devices,lubrication and tribology,drug delivery systems,and environmental remediation.This work studies nanofluid flow over a viscoelastic boundary layer,focusing on mass and heat transmission.An analysis is performed on the flow traversing a porous sheet undergoing nonlinear stretching.It assesses the consequences of viscous dissipation and thermal radiation.The scientific nanofluid framework laid out by Buongiorno has been exploited.The partial differential equations illustrating the phenomena can be transfigured into ordinary differential equations by utilizing appropriate similarity transformations.The simplified equations are unmasked using the Homotopy Analysis Method(HAM),a semi-analytical approach designed to solve nonlinear ordinary and partial differential equations commonly encountered in numerous scientific and engineering disciplines.Calculations are executed to ascertain the numerical solutions related to temperature,concentration,and velocity fields,accompanied by the skin friction coefficient,local Nusselt number,and local Sherwood number.Visualizations of the results are accompanied by pertinent explanations grounded in scientific principles.The temperature distribution and corresponding thermal layer have been enhanced due to radiative and viscous dissipation characteristics.Additionally,it has been noted that a delay in fluid movement results from an improvement in the porous medium parameter and magnetic field values.A falling trend in the Nusselt number is observed as the Eckert and thermophoresis parameters increase.The current numerical results have been effectively validated against previous difficulties.展开更多
Polymer flooding is an important means of improving oil recovery and is widely used in Daqing,Xinjiang,and Shengli oilfields,China.Different from conventional injection media such as water and gas,viscoelastic polymer...Polymer flooding is an important means of improving oil recovery and is widely used in Daqing,Xinjiang,and Shengli oilfields,China.Different from conventional injection media such as water and gas,viscoelastic polymer solutions exhibit non-Newtonian and nonlinear flow behavior including shear thinning and shear thickening,polymer convection,diffusion,adsorption,retention,inaccessible pore volume,and reduced effective permeability.However,available well test model of polymer flooding wells generally simplifies these characteristics on pressure transient response,which may lead to inaccurate results.This work proposes a novel two-phase numerical well test model to better describe the polymer viscoelasticity and nonlinear flow behavior.Different influence factors that related to near-well blockage during polymer flooding process,including the degree of blockage(inner zone permeability),the extent of blockage(composite radius),and polymer flooding front radius are explored to investigate these impacts on bottom hole pressure responses.Results show that polymer viscoelasticity has a significant impact on the transitional flow segment of type curves,and the effects of near-well formation blockage and polymer concentration distribution on well test curves are very similar.Thus,to accurately interpret the degree of near-well blockage in injection wells,it is essential to first eliminate the influence of polymer viscoelasticity.Finally,a field case is comprehensively analyzed and discussed to illustrate the applicability of the proposed model.展开更多
As oil and gas development increasingly targets unconventional reservoirs,the limitations of conventional hydraulic fracturing,namely high water consumption and significant reservoir damage,have become more pronounced...As oil and gas development increasingly targets unconventional reservoirs,the limitations of conventional hydraulic fracturing,namely high water consumption and significant reservoir damage,have become more pronounced.This has driven growing interest in the development of clean fracturing fluids that minimize both water usage and formation impairment.In this study,a low-liquid-content viscoelastic surfactant(VES)foam fracturing fluid system was formulated and evaluated through laboratory experiments.The optimized formulation comprises 0.2%foaming agent CTAB(cetyltrimethylammonium bromide)and 2%foam stabilizer EAPB(erucamidopropyl betaine).Laboratory tests demonstrated that the VES foam system achieved a composite foam value of 56,700 mL・s,reflecting excellent foaming performance.Proppant transport experiments revealed minimal variation in suspended sand volume over 120 min across different sand ratios,indicating robust sand-carrying capacity even at high proppant concentrations.Rheological measurements showed that the fluid maintained a viscosity above 120 mPa・s after 120 min of shearing at 70℃ and a shear rate of 170 s−1,with the elastic modulus exceeding the viscous modulus,confirming the system’s exceptional stability and resilience.Furthermore,core damage tests indicated that the VES foam caused only 4.42%formation damage,highlighting its potential for efficient and low-damage stimulation of tight reservoirs.Overall,the findings demonstrate that this low-liquid-content VES foam provides a highly effective,environmentally considerate alternative for hydraulic fracturing in unconventional formations,combining superior proppant transport,rheological stability,and minimal reservoir impairment.展开更多
基金National Natural Science Foundation of China under Grant Nos.51979205 and 51939008。
文摘This research is focused on the calculation of a reasonable detonator delay time for realizing cut blast vibration control.First,the viscoelastic rock mass parameters corresponding to the engineering rock mass quality classification were determined based on wave theory of Kelvin medium.Then,a calculation model was obtained for the millisecond-delay cut blast vibration in Kelvin media using the Starfield charge superposition principle.Further,the influence of the delay time on the cut blast vibration was quantitatively analyzed and a method for calculating the reasonable cut blasting millisecond delay time is proposed according to the principle of dimensional analysis.Finally,field tests were used to verify the applicability of the method.The results show that 5 ms to 20 ms is a better detonator delay time range and cut blasting vibration can be effectively controlled using the delay time calculated by the calculation model described in this paper.
基金funded by Vale S.A.company(www.vale.com)and the Institute of Technology Vale(ITV—www.itv.org),grant number SAP 4600048682.
文摘The roller is one of the fundamental elements of ore belt conveyor systems since it supports,guides,and directs material on the belt.This component comprises a body(the external tube)that rotates around a fixed shaft supported by easels.The external tube and shaft of rollers used in ore conveyor belts are mostly made of steel,resulting in high mass,hindering maintenance and replacement.Aiming to achieve mass reduction,we conducted a structural optimization of a roller with a polymeric external tube(hereafter referred to as a polymeric roller),seeking the optimal values for two design parameters:the inner diameter of the external tube and the shaft diameter.The optimization was constrained by admissible values for maximum stress,maximum deflection and misalignment angle between the shaft and bearings.A finite element model was built in Ansys Workbench to obtain the structural response of the system.The roller considered is composed of an external tube made of high-density polyethylene(HDPE),bearing seats of polyamide 6(PA6),and a steel shaft.To characterize the polymeric materials(HDPE and PA6),stress relaxation tests were conducted,and the data on shear modulus variation over time were inserted into the model to calculate Prony series terms to account for viscoelastic effects.The roller optimization was performed using surrogate modeling based on radial basis functions,with the Globalized Bounded Nelder-Mead(GBNM)algorithm as the optimizer.Two optimization cases were conducted.In the first case,concerning the roller’s initial material settings,the designs found violated the constraints and could not reduce mass.In the second case,by using PA6 in both bearing seats and the tube,a design configuration was found that respected all constraints and reduced the roller mass by 15.5%,equivalent to 5.15 kg.This study is among the first to integrate experimentally obtained viscoelastic data into the surrogate-based optimization of polymeric rollers,combining methodological innovation with industrial relevance.
基金supported by the National Natural Science Foundation of China(Nos.42174074,and 41674055).
文摘We investigated the influence of historical earthquakes on the 2022 Luding M_(S)6.8 earthquake and its subsequent effects.We computed the viscoelastic Coulomb stress changes induced by these historical seismic events using the rupture model of historical earthquakes and the layered Maxwell viscoelastic medium model.Our findings indicate that the Luding earthquake was brought forward approximately 29 years because of several historical earthquakes.Specifically,the 1923 Renda M_(S)7.3 earthquake,the 1933 Diexi M_(S)7.5 earthquake,the 1973 Luhuo M_(S)7.3 earthquake,the 2008 Kangding M_(S)5.1 earthquake,the 2008 Wenchuan M_(S)8.0 earthquake,the 2014 Kangding M_(S)6.3 earthquake,and the 2014 Kangding M_(S)5.8 earthquake advanced the occurrence of the event by 117.61,26.67,84.51,0.27,0.91,7.64,and 3.17 years,respectively.Conversely,the 1936 Mabian earthquake swarm,the 1948 Litang M_(S)7.3 earthquake,the 1955 Kangding M_(S)7.5 earthquake,and the 2013 Lushan M_(S)7.0 earthquake delayed its occurrence by 39.89,22.43,144.23,and 4.89 years,respectively.Furthermore,by employing the halfspace homogeneous elastic model and the rupture characteristics of the Luding earthquake,we computed the coseismic Coulomb stress changes in neighboring faults.Our results reveal increased Coulomb stress on the Xianshuihe fault(excluding its southern segment),the Anninghe fault,the Zemuhe fault,the Daliangshan fault,the southern segment of the Longmenshan fault,the northern segment of the Mabian-Yanjin fault,and the Xiaojinhe fault.Conversely,we observed stress decreases in the southern segment of the Jinshajiang fault,the central and eastern segments of the Longriba fault,the Mabian-Yanjin fault(excluding its northern segment),and the southern segment of the Xianshuihe fault.
基金jointly funded by the Strategic Priority Research Program of the Chinese Academy of Sciences(grant No.XDA0430301)the National Natural Science Foundation of China(grant Nos.42130109,41973059)。
文摘The formation of copper deposits is closely related to hydrothermal processes.Understanding the migration of copper in hydrothermal fluids aids in reconstructing mineralization processes and deciphering deposit genesis.Copper primarily exists as Cu^(+)and Cu^(2+)in hydrothermal solutions,with redox conditions governing their interconversion.In chloride-rich geological fluids,Cu-Cl complexes are considered critical for copper transport.However,the specific types and valence transitions of Cu-Cl complexes under varying hydrothermal conditions remain poorly understood.This study employed in situ Raman spectroscopy to systematically analyze Cu+HCl and CuCl_(2)+K_(2)S_(2)O_(3)/H_(2) systems under saturated vapor pressure at 25-300℃,elucidating the effects of temperature,Cl^(-)concentration,and redox conditions on copper speciation.In the Cu^(+)HCl system,copper dissolved as monovalent Cu-Cl complexes.At high temperatures(>200℃),[CuCl_(2)]^(-)is the dominated species,whereas[CuCl_(3)]^(2-)becomes prevalent at lower temperatures and higher HCl concentrations.For the Cu^(2+)-Cl system,the dominant species transitioned from[Cu(H_(2)O)n]^(2+)(<50℃)to[CuCl_(4)]^(2-)(100℃)and further to[CuCl]^(+)and[CuCl_(2)]^(0) at 300℃.The introduction of reducing agents(K_(2)S_(2)O_(3)/H_(2))facilitated Cu^(2+)→Cu^(+)reduction,thereby stabilizing Cu^(+)-Cl complexes and inducing partial copper precipitation.The behavior of copper in chloriderich hydrothermal fluids observed in this study indicates that high-temperature oxidizing fluids facilitate Cu mobilization,while cooling and redox changes promote deposition and ore minerals formation.
文摘This study presents and verifies a hybrid methodology for reliable determination of parameters in structural rheological models(Zener,Burgers,and Maxwell)describing the viscoelastic behavior of polyurethane specimens manufactured using extrusion-based 3D printing.Through comprehensive testing,including cyclic compression at strain rates ranging from 0.12 to 120 mm/min(0%-15%strain)and creep/relaxation experiments(10%-30%strain),the lumped parameters were independently determined using both analytical and numerical solutions of the models’differential equations,followed by cross-verification in additional experiments.Numerical solutions for creep and relaxation problems were obtained using finite element analysis,with the three-parameter Mooney-Rivlin model and Prony series employed to simulate elastic and viscous stress components,respectively.Energy dissipation per cycle was quantified during cyclic compression tests.The results demonstrate that all three models adequately describe material behavior within the 0%-15%strain range across various strain rates.Comparative analysis revealed the Burgers model’s superior performance in characterizing creep and stress relaxation at low strain levels.While Zener and Burgers model parameters from uniaxial compression showed limited applicability for energy dissipation calculations,the generalized Maxwell model effectively captured viscoelastic properties across different strain rates.Notably,parameters derived from creep tests provided a more universal assessment of dissipative properties due to optimization based on characteristic curve regions.Both parameter sets described polyurethane’s elastic-hysteretic behavior with approximately 20%error,proving significantly more accurate than the linear strain-time dependence hypothesis.Finite element analysis(FEA)complemented numerical modeling by demonstrating that while the generalized Maxwell model effectively describes initial rapid stress-strain changes,FEA provides superior characterization of steady-state processes.This computational approach yields more physically representative results compared to simplified analytical solutions,despite certain limitations in transient analysis.
基金funded by National Natural Science Foundation of China(42373033,Yicheng Sun)Fundamental Research Funds for the Central Universities(B240201111,Yicheng Sun)。
文摘Supercritical fluids play a crucial role in material transport within Earth's deep interior.Investigating the pressure-dependent atomic structures and transport properties of such fluids is essential for understanding their petrological,chemical,and geophysical behaviors.In this study,we employed first-principles molecular dynamics simulations to explore the structures,self-diffusion coefficients(D),and viscosities(η)of supercritical NaAlSi_(3)O_(8)-H_(2)O fluids under conditions of 2000 K and 3-10 GPa,with water contents of 30 wt% and 50 wt%.Our calculations indicate that at a water content of 30 wt%,Q^(2) and Q^(3) exhibit a certain degree of positive and negative pressure dependence,respectively,while other Q^(n) species(n represents the number of bridging oxygens connected to Si/Al)show minimal changes.At a water content of 50 wt%,Q^(2) and Q^(0) exhibit a certain degree of positive and negative pressure dependence,respectively,while other Q^(n) species show minimal changes.At both water contents,Si-O-H and molecular water in the system exhibit negative pressure dependence,suggesting that the migration of supercritical fluids from deep to shallow regions is accompanied by the release of water.The self-diffusion coefficients in the supercritical NaAlSi_(3)O_(8)-H_(2)O fluid follow the order D_(Na)≈D_(H)>D_(O)>D_(Al)≈D_(Si),with an overall weak negative pressure dependence.By comparing the viscosities of anhydrous and hydrous silicate melts from previous studies,we found that the addition of water caused a transition from negative to positive pressure dependence of viscosity,corresponding to a structural change from polymerization to depolymerization.Additionally,we calculated the fluid mobility Δp/η of supercritical NaAlSi_(3)O_(8)-H_(2)O fluids and found that their mobility is several orders of magnitude higher than that of basalt melt and is also significantly greater than that of carbonate melt.As supercritical fluids ascend from deeper to shallower regions,their mobility is further enhanced,significantly contributing to the transport of elements from subducting slabs to the overlying mantle wedge.
文摘1 INTRODUCTIONIt is well known that viscoelasticity and thixotropy of fluids are often investigated by measuringhysteresis loops under transient conditions.For some fluids(such as blood),it has been provedthat,an“8”shaped hysteresis loop may be obtained if triangular steps of shear rate wereapplied on it(Fig.l).This kind of hysteresis loop is composed of a viscoelastic loop and athixotropic loop.The viscoelastic and thixotropic properties are unified in the formation ofthe hysteresis loop.How to describe the formation of this complex hysteresis loop and how
基金supported by the National Natural Science Foundation of China(No.11902165)the Natural Science Foundation of Inner Mongolia Autonomous Region of China(No.2019BS01004)。
文摘This study investigates the electromagnetohydrodynamic(EMHD)flow of fractional viscoelastic fluids through a microchannel under the Navier slip boundary condition.The flow is driven by the pressure gradient and electromagnetic force where the electric field is applied horizontally,and the magnetic field is vertically(upward or downward).When the electric field direction is consistent with the pressure gradient direction,the changes of the steady flow rate and velocity with the Hartmann number Ha are irrelevant to the direction of the magnetic field(upward or downward).The steady flow rate decreases monotonically to zero with the increase in Ha.In contrast,when the direction of the electric field differs from the pressure gradient direction,the flow behavior depends on the direction of the magnetic field,i.e.,symmetry breaking occurs.Specifically,when the magnetic field is vertically upward,the steady flow rate increases first and then decreases with Ha.When the magnetic field is reversed,the steady flow rate first reduces to zero as Ha increases from zero.As Ha continues to increase,the steady flow rate(velocity)increases in the opposite direction and then decreases,and finally drops to zero for larger Ha.The increase in the fractional calculus parameterαor Deborah number De makes it take longer for the flow rate(velocity)to reach the steady state.In addition,the increase in the strength of the magnetic field or electric field,or in the pressure gradient tends to accelerate the slip velocity at the walls.On the other hand,the increase in the thickness of the electric double-layer tends to reduce it.
文摘Four typical types of residual oil, residual oil trapped in dead ends, oil ganglia in pore throats, oil at pore corners and oil film adhered to pore walls, were studied. According to main pore structure characteristics and the fundamental morphological features of residual oil, four displacement models for residual oil were proposed, in which pore-scale flow behavior of viscoelastic fluid was analyzed by a numerical method and micro-mechanisms for mobilization of residual oil were discussed. Calculated results indicate that the viscoelastic effect enhances micro displacement efficiency and increases swept volume. For residual oil trapped in dead ends, the flow field of viscoelastic fluid is developed in dead ends more deeply, resulting in more contact with oil by the displacing fluid, and consequently increasing swept volume. In addition, intense viscoelastic vortex has great stress, under which residual oil becomes small oil ganglia, and finally be carried into main channels. For residual oil at pore throats, its displacement mechanisms are similar to the oil trapped in dead ends. Vortices are developed in the depths of the throats and oil ganglia become smaller. Besides, viscoelastic fluid causes higher pressure drop on oil ganglia, as a driving force, which can overcome capillary force, consequently, flow direction can be changed and the displacing fluid enter smaller throats. For oil at pore corners, viscoelastic fluid can enhance displacement efficiency as a result of greater velocity and stress near the corners. For residual oil adhered to pore wall, viscoelastic fluid can provide a greater displacing force on the interface between viscoelastic fluid and oil, thus, making it easier to exceed the minimum interfacial tension for mobilizing the oil film.
基金Project supported by the China Postdoctoral Science Foundation(Grant No.2011M500652)the National Natural Science Foundation of China(Grant Nos.51276046 and 51206033)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20112302110020)
文摘A mixed subgrid-scale（SGS） model based on coherent structures and temporal approximate deconvolution（MCT） is proposed for turbulent drag-reducing flows of viscoelastic fluids. The main idea of the MCT SGS model is to perform spatial filtering for the momentum equation and temporal filtering for the conformation tensor transport equation of turbulent flow of viscoelastic fluid, respectively. The MCT model is suitable for large eddy simulation（LES） of turbulent dragreducing flows of viscoelastic fluids in engineering applications since the model parameters can be easily obtained. The LES of forced homogeneous isotropic turbulence（FHIT） with polymer additives and turbulent channel flow with surfactant additives based on MCT SGS model shows excellent agreements with direct numerical simulation（DNS） results. Compared with the LES results using the temporal approximate deconvolution model（TADM） for FHIT with polymer additives, this mixed SGS model MCT behaves better, regarding the enhancement of calculating parameters such as the Reynolds number.For scientific and engineering research, turbulent flows at high Reynolds numbers are expected, so the MCT model can be a more suitable model for the LES of turbulent drag-reducing flows of viscoelastic fluid with polymer or surfactant additives.
基金supported by the National Natural Science Foundation of China(Grant No.11632016).
文摘Particle motion in confined shear flow of viscoelastic fluids is very common in nature and has a wide range of applications.Understanding and mastering the motion characteristics of particles in viscoelastic fluids has important academic value and practical significance.In this paper,we first introduce the related equations and characteristic parameter,and then emphasize the following issues:the lateral equilibrium position of particle;interaction and aggregation of multiple particles;the chain structure formed by multiple particles;and the motion of non-spherical particle.Finally,some unresolved issues,challenges,and future research directions are highlighted.
基金R.Zi is partially supported by the National Natural Science Foundation of China(11871236 and 11971193)the Natural Science Foundation of Hubei Province(2018CFB665)the Fundamental Research Funds for the Central Universities(CCNU19QN084).
文摘Some sufficient conditions of the energy conservation for weak solutions of incompressible viscoelastic flows are given in this paper.First,for a periodic domain in R^(3),and the coefficient of viscosity μ=0,energy conservation is proved for u and F in certain Besovs paces.Furthermore,in the whole space R^(3),it is shown that the conditions on the velocity u and the deformation tensor F can be relaxed,that is,u∈B_(3,c(N))^(1/3),and F∈B_(3,∞)^(1/3).Finally,when μ>0,in a periodic domain in R^(d) again,a result independent of the spacial dimension is established.More precisely,it is shown that the energy is conserved for u∈L^(T)(0,T;L^(n)(Ω))for any 1/r+1/s≤1/2,with s≥4,and F∈L^(m)(0,T;L^(n)(Ω))for any 1/m+1/n≤1/2,with n≥4.
基金supported by Grant Agency of the Charles University(454213)
文摘We prove a local existence of a strong solution v ：Ω×T→R^3 for a system of nonlinear integrodifferential equations describing motion of an incompressible viscoelastic fluid using standard mathematical tools. The problem is considered in a bounded, smooth domain ΩСR^3 with a Dirichlet boundary condition and a standard initial condition.
基金Supported by the National Natural Science Foundation of China under Grant No 10972117.
文摘A new generalized Lorenz system is presented based on the thermal convection of Oldroyd-B fluids in a circular loop. Two non-dimensional parameters De1 （a measure of the fluid relaxation） and De2 （a measure of the fluid retardation） appear in the equation. Then we study this generalized Lorenz equation numerically and find that the values of De1 and De2 can greatly influence the behavior of the solution. The fluid relaxation De1 is found to precipitate the onset of periodic solution （limit cycle） in the system and impedes the onset of chaos while the fluid retardation （De2） tends to delay the onset of the periodic solution and precipitate the onset of chaos in the system.
基金funded by Fondo Francisco Jose de Caldas,MINCIENCIAS and Agencia Nacional de hidrocarburos(ANH)through contract No.112721-282-2023(Project 1118-1035-9300)with Universidad Nacional de Colombia-Sede Medellin and PAREX RESOURCES COLOMBIA AG SUCURSAL。
文摘The conservation of rheological and filtration properties of drilling fluids is essential during drilling operations.However,high-pressure and high-temperature conditions may affect drilling fluid additives,leading to their degradation and reduced performance during operation.Hence,the main objective of this study is to formulate and evaluate a viscoelastic surfactant(VES)to design water-based drilling nanofluids(DNF).Silica nanomaterials are also incorporated into fluids to improve their main functional characteristics under harsh conditions.The investigation included:i)synthesis and characterization of VES through zeta potential,thermogravimetric analysis(TGA),Fourier transform infrared spectroscopy(FTIR),atomic force microscopy(AFM),and rheological behavior;ii)the effect of the presence of VES combined with silica nanoparticles on the rheological,filtration,thermal,and structural properties by steady and dynamic shear rheological,filter press,thermal aging assays,and SEM(SEM)assays,respectively;and iii)evaluation of filtration properties at the pore scale through a microfluidic approach.The rheological results showed that water-based muds(WBMs)in the presence of VES exhibited shearthinning and viscoelastic behavior slightly higher than that of WBMs with xanthan gum(XGD).Furthermore,the filtration and thermal properties of the drilling fluid improved in the presence of VES and silica nanoparticles at 0.1 wt%.Compared to the WBMs based on XGD,the 30-min filtrate volume for DNF was reduced by 75%.Moreover,the Herschel-Bulkley model was employed to represent the rheological behavior of fluids with an R2of approximately 0.99.According to SEM,laminar and spherical microstructures were observed for the WBMs based on VES and XGD,respectively.A uniform distribution of the nanoparticles was observed in the WBMs.The results obtained from microfluidic experiments indicated low dynamic filtration for fluids containing VES and silica nanoparticles.Specifically,the filtrate volume of fluids containing VES and VES with silica nanoparticles at 281 min was 0.35 and 0.04 m L,respectively.The differences in the rheological,filtration,thermal,and structural results were mainly associated with the morphological structure of VES or XGD and surface interactions with other WBMs additives.
文摘This paper presents ordered rate nonlinear constitutive theories for thermoviscoelastic fluids based on Classical Continuum Mechanics (CCM). We refer to these fluids as classical thermoviscoelastic polymeric fluids. The conservation and balance laws of CCM constitute the core of the mathematical model. Constitutive theories for the Cauchy stress tensor are derived using the conjugate pair in the entropy inequality, additional desired physics, and the representation theorem. The constitutive theories for the Cauchy stress tensor consider convected time derivatives of Green’s strain tensor or the Almansi strain tensor up to order n and the convected time derivatives of the Cauchy stress tensor up to order m. The resulting constitutive theories of order (m, n) are based on integrity and are valid for dilute as well as dense polymeric, compressible, and incompressible fluids with variable material coefficients. It is shown that Maxwell, Oldroyd-B, and Giesekus constitutive models can be described by a single constitutive theory. It is well established that the currently used Maxwell and Oldroyd-B models predict zero normal stress perpendicular to the flow direction. It is shown that this deficiency is a consequence of not retaining certain generators and invariants from the integrity (complete basis) in the constitutive theory and can be corrected by including additional generators and invariants in the constitutive theory. Similar improvements are also suggested for the Giesekus constitutive model. Model problem studies are presented for BVPs consisting of fully developed flow between parallel plates and lid-driven cavities utilizing the new constitutive theories for Maxwell, Oldroyd-B, and Giesekus fluids. Results are compared with those obtained from using currently used constitutive theories for the three polymeric fluids.
文摘The paper explores the gravity-driven flow of the thin film of a viscoelastic-fluid-based nanofluids(VFBN)along an inclined plane under non-isothermal conditions and subjected to convective cooling at the free-surface.The Newton’s law of cooling is used to model the convective heat-exchange with the ambient at the free-surface.The Giesekus viscoelastic constitutive model,with appropriate modifications to account for non-isothermal effects,is employed to describe the polymeric effects.The unsteady and coupled non-linear partial differential equations(PDEs)describing the model problem are obtained and solved via efficient semi-implicit numerical schemes based on finite difference methods(FDM)implemented in Matlab.The response of the VFBN velocity,temperature,thermal-conductivity and polymeric-stresses to variations in the volume-fraction of embedded nanoparticles is investigated.It is shown that these quantities all increase as the nanoparticle volume-fraction becomes higher.
文摘Viscoelastic nanofluid flow has drawn substantial interest due to its industrial uses,including research and testing of medical devices,lubrication and tribology,drug delivery systems,and environmental remediation.This work studies nanofluid flow over a viscoelastic boundary layer,focusing on mass and heat transmission.An analysis is performed on the flow traversing a porous sheet undergoing nonlinear stretching.It assesses the consequences of viscous dissipation and thermal radiation.The scientific nanofluid framework laid out by Buongiorno has been exploited.The partial differential equations illustrating the phenomena can be transfigured into ordinary differential equations by utilizing appropriate similarity transformations.The simplified equations are unmasked using the Homotopy Analysis Method(HAM),a semi-analytical approach designed to solve nonlinear ordinary and partial differential equations commonly encountered in numerous scientific and engineering disciplines.Calculations are executed to ascertain the numerical solutions related to temperature,concentration,and velocity fields,accompanied by the skin friction coefficient,local Nusselt number,and local Sherwood number.Visualizations of the results are accompanied by pertinent explanations grounded in scientific principles.The temperature distribution and corresponding thermal layer have been enhanced due to radiative and viscous dissipation characteristics.Additionally,it has been noted that a delay in fluid movement results from an improvement in the porous medium parameter and magnetic field values.A falling trend in the Nusselt number is observed as the Eckert and thermophoresis parameters increase.The current numerical results have been effectively validated against previous difficulties.
基金supported by the National Natural Science Foundation of China(52104049)the Young Elite Scientist Sponsorship Program by Beijing Association for Science and Technology(BYESS2023262)。
文摘Polymer flooding is an important means of improving oil recovery and is widely used in Daqing,Xinjiang,and Shengli oilfields,China.Different from conventional injection media such as water and gas,viscoelastic polymer solutions exhibit non-Newtonian and nonlinear flow behavior including shear thinning and shear thickening,polymer convection,diffusion,adsorption,retention,inaccessible pore volume,and reduced effective permeability.However,available well test model of polymer flooding wells generally simplifies these characteristics on pressure transient response,which may lead to inaccurate results.This work proposes a novel two-phase numerical well test model to better describe the polymer viscoelasticity and nonlinear flow behavior.Different influence factors that related to near-well blockage during polymer flooding process,including the degree of blockage(inner zone permeability),the extent of blockage(composite radius),and polymer flooding front radius are explored to investigate these impacts on bottom hole pressure responses.Results show that polymer viscoelasticity has a significant impact on the transitional flow segment of type curves,and the effects of near-well formation blockage and polymer concentration distribution on well test curves are very similar.Thus,to accurately interpret the degree of near-well blockage in injection wells,it is essential to first eliminate the influence of polymer viscoelasticity.Finally,a field case is comprehensively analyzed and discussed to illustrate the applicability of the proposed model.
文摘As oil and gas development increasingly targets unconventional reservoirs,the limitations of conventional hydraulic fracturing,namely high water consumption and significant reservoir damage,have become more pronounced.This has driven growing interest in the development of clean fracturing fluids that minimize both water usage and formation impairment.In this study,a low-liquid-content viscoelastic surfactant(VES)foam fracturing fluid system was formulated and evaluated through laboratory experiments.The optimized formulation comprises 0.2%foaming agent CTAB(cetyltrimethylammonium bromide)and 2%foam stabilizer EAPB(erucamidopropyl betaine).Laboratory tests demonstrated that the VES foam system achieved a composite foam value of 56,700 mL・s,reflecting excellent foaming performance.Proppant transport experiments revealed minimal variation in suspended sand volume over 120 min across different sand ratios,indicating robust sand-carrying capacity even at high proppant concentrations.Rheological measurements showed that the fluid maintained a viscosity above 120 mPa・s after 120 min of shearing at 70℃ and a shear rate of 170 s−1,with the elastic modulus exceeding the viscous modulus,confirming the system’s exceptional stability and resilience.Furthermore,core damage tests indicated that the VES foam caused only 4.42%formation damage,highlighting its potential for efficient and low-damage stimulation of tight reservoirs.Overall,the findings demonstrate that this low-liquid-content VES foam provides a highly effective,environmentally considerate alternative for hydraulic fracturing in unconventional formations,combining superior proppant transport,rheological stability,and minimal reservoir impairment.
